Light emitting diode (LED) is a semiconductor light emitting device and has been widely used in indicator light and display screen and so on. White light emitting diode is the third-generation lighting source after the incandescent electric light and the fluorescent electric light, has become the target that lamp fixture and light source research institutions around the world are racing to develop and acquire, and is a popular industry of the future in lighting field.
Since the successful development of metal-organic chemical epitaxial growth technology, AlGaInP based materials are undergoing a rapid development and used for producing high power and high brightness red and yellow light emitting diodes. Although red light emitting diodes with AlGaInP based materials have been commercially produced and the light emitting diode with four-element (also referred to as “quaternary”) alloy material as the multi-quantum well active region has a very high internal quantum efficiency, due to the restriction of the material itself and the substrate, the external quantum efficiency of conventional AlGaInP-LED is very low. A major reason for the poor light emitting efficiency of the conventional AlGaInP-LED is that the GaAs substrate is light-absorbing material, resulting in the absorption of a great amount of light by the GaAs substrate radiated from the active layer (MQW) to the direction of the substrate, and even the metal omni-directional reflector with the support of substrate transfer technology has been developed to replace the conventional GaAs substrate, the losses in a fixed percentage of the light radiated and reflected to the active layer still occur.